This project aims to develop a new class of products based on novel, tissue-equivalent gels that can be used to produce highly-resolved and accurate data on three dimensional radiation dose distributions using magnetic resonance imaging (MRI), using much less time of radiation therapy equipment that existing techniques, and at a much lower cost. The dose-response mechanism relies on radiation-induced formation of a polymer in a gel, which increases water proton NMR relaxation rates in proportion to absorbed dose. The polymer-gel dosimeter is stable and can be imaged with delays of even several months without any loss of the dose data. The gel will find widespread use in radiation therapy practice, for 3D measurements in homogeneous and anthropomorphic phantoms, confirmation of computerized treatment planning and in quality assurance procedures. The goals of Phase II are to complete the development of the method, with special emphasis on developing reliable processes of gel preparation, on minimizing the costs of manufacturing and usage of the gels, and the characterization of dosimeter performance, from radiation response to MR imaging of dose distributions. It is anticipated that a commercially viable product will be developed at the completion of the Phase II. PROPOSED COMMERCIAL APPLICATION: (Annual domestic market) Acceptance testing of approximately 125 new high energy X-ray machines requires the measurement of between 6 and 12 dose distributions, using about 1,200 gels. Quality assurance procedures for the existing 2,500 linear accelerators could require 10,000 polymer-gels. Brachytherapy and experimental applications could account for 2,000 more gels. At least $200 per gel, initial annual sales in excess of $2.5 million are anticipated.